1. Technical Field
This disclosure relates to a double-side image formation method applicable to image formation apparatuses such as a laser beam printer (page printer), a copying machine, a facsimile apparatus, and a multifunction machine; and an image formation apparatus for realizing the method.
2. Description of the Related Art
[Background Technique]
As a double-side image formation method of the image formation apparatuses (such as a laser beam printer and a copying machine) that include a reversing unit and an image formation unit along a conveyance way of a recording medium such as paper, the image formation unit forms an image on one side of a recording medium that is fed from a feed unit, the reversing unit returns the recording medium to the image formation unit, and an image is formed on the other side of the recording medium. More specifically, for example, when 30 sheets of the recording medium (paper), i.e., 60 pages, are to be copied, 30 pages are first copied on one side of the sheets, and the 30 sheets are stacked on a middle tray through the reversing unit. Then, the stacked recording media are provided to the image formation unit one by one, and the other 30 pages are copied onto their other side (for example, Patent Reference 1). This double-side image formation method is called a stack mode method.
Another double-side image formation method is called an inter-leaf method that is intended to raise productivity of double-side image formation. When a manuscript that includes two or more sheets, where each sheet bears an image to be copied only on one side, is to be copied to both sides of the recording media for two or more copies, the inter-leaf method realizes 100% double-side image formation productivity by removing losses not only in a last phase but also in early stages. In other words, the time required for one-side image formation is the same as time required for double-side image formation. In order to realize high productivity, Patent Reference 2 proposes a double-side image formation apparatus
wherein the number of inter-leaf sheets, only one side of which sheets is continuously recorded (printed) at the time of recording start, is n,
the apparatus is capable of storing at least (2n−1) sheets of the recording medium in a double-side conveyance path, through which path the recording media are conveyed when double-side recording is performed, wherein
in the early stages until inter-leaf control is started, copying onto only one side of x sheets of the recording medium is continuously performed, where n<x<=2n−1,
then, copying onto the other side of y sheets of the recording medium is continuously performed, where y=x−n+1, and
then, the inter-leaf control for n sheets is performed.
Further, Patent Reference 3 discloses a technique of the inter-leaf control for further raising the double-side image formation productivity by reducing losses in a final paper process. There, recording information that sequentially continues for every page is stored, and recording information for two pages is recorded on each side of a recording medium out of all the stored recording information. According to the technique, the inter-leaf control is performed for alternately printing (copying) onto a recording medium, one side of which recording medium has been printed, and a new recording medium. There, if the number of sheets of the recording medium, the first page of which recording medium is continuously printed in the beginning is n, the number of sheets of the recording medium, the first page of which recording medium is continuously printed in the last phase is n+1.
[Patent Reference 1] JP 3002216
[Patent Reference 2] JPA 2001-326786
[Patent Reference 3] JPA 2001-322317
An inter-leaf operation is for preventing the productivity of double-side printing from being degraded as described above. Properties of the inter-leaf operation are dependent on sheet length, conveyance path length, and productivity (space/interval between sheets). The inter-leaf operations disclosed by Patent References 2 and 3 take the number of inter-leaf sheets into consideration; however, the sheet length, the conveyance path length, and the productivity are not considered.